CINCINNATI – The champagne was spraying, the players were screaming and star catcher Buster Posey was chasing teammate Jeremy Affeldt through the plastic-wrapped San Francisco Giants clubhouse on Thursday. Posey got Affeldt good. Then Affeldt popped a cork and retaliated, the bubbly gushing like water from a fire hose. It was chaotic and joyous, and there was Posey, right in the middle of it, again.

For all the talk of pregame speeches and dugout mosh pits, they were not the real reasons the Giants came back against the Cincinnati Reds in this National League Division Series – losing the first two at home, then winning the next three on the road to take the series, something that had never been done before.

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This is not high school football. This is big league baseball. It was not so much emotion as it was execution, in big moments and little moments – hitting a grand slam, gunning down runners at third.

There is no doubt about the defining moment of Thursday's 6-4 victory. It came in the top of the fifth, when Posey came to the plate to face Mat Latos with the bases loaded. He was in a 1-for-12 minifunk, but he was still the same guy who led the National League in hitting, still the wrong guy to give a 94-mph fastball down the middle with the season on the line.

"I was able to get a pitch in the zone and got the barrel on it," Posey said, "and good things happened."

Posey smoked it.

Before he finished his beautiful, violent swing, Reds catcher Ryan Hanigan dropped his glove between his legs, drooped his shoulders and walked off to the right, unwilling to watch. Before the ball reached its apex, somebody in the press box said: "Ballgame." The stadium stood silent as the ball ricocheted off the upper deck in left field and dropped back onto the grass. You could hear shouts of profanity from the fans as Posey rounded the bases and returned to his high-fiving teammates.

Now, it wasn't the ballgame, and if anyone should have known, it was the scribes who had been watching this series play out. The score was 6-0. That was hardly insurmountable for the Reds, considering what the Giants had already overcome.

The Giants were awful in San Francisco. Couldn't pitch. Couldn't hit. They were outscored, 14-2. They looked nothing like a team about to turn it around, especially in Cincinnati, where they often struggled and the Reds hadn't lost three in a row all season.

Manager Bruce Bochy tried to make them believe before Game 3. He had played for the 1984 San Diego Padres, who rallied from a 2-0 deficit to beat the Chicago Cubs in the NL Championship Series, back when it was best of five. He told the Bible story of how Gideon won a battle even though he was outnumbered by the Midianites.

"This is a spiritual group," said Giants coach Tim Flannery, who also played on those 1984 Padres. "It's good that they at least understand the first miracle of Jesus was turning water to wine, because they're all drinking tonight."

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It's a good story. So is Hunter Pence chiming in after Bochy, telling his teammates in the clubhouse that he wanted to play one more game with them, then gathered them in the dugout to link arms and jump around and pump up. They did the dugout mosh pit before Game 4. They did it again before Game 5.

"Without him and his want and will power, I'm not sure we would have done this," Posey said. "He rallied us."

But if you really want to find the first snowflake of the snowball, dig down to bottom of the first of Game 3. The Reds' Brandon Phillips took off to steal second. There was a wild pitch. Phillips tried to take third, too. But Posey grabbed the ball off the backstop and gunned him down, which ended up saving a run.

Remember, Game 3 was 1-1 after nine innings. The Giants had only one hit at that point. They had not held a lead in 27 innings. They were one run from being swept. They ended up winning that game and staying alive because Posey saved that run and because the Reds gave them another one with a passed ball and an error in the 10th.

The Giants won Game 4, 8-3. Posey's grand slam gave them that 6-0 lead in Game 5. They looked alive again.

Still, the Reds cut the lead to 6-3 in the sixth, and they brought the tying run to the plate with no one out. Reds manager Dusty Baker called for a double steal to avoid a double play – one of many moves for which he will be second-guessed – and it backfired. Hanigan took a called third strike, and even though he double-clutched, Posey completed a double play by gunning out Jay Bruce at third.

The Giants got out of it. They got out of it again and again, as the Reds brought the tying run to the plate in the seventh, eighth and ninth – and the winning run to the plate in the ninth. Angel Pagan made a diving catch in center to rob Dioner Novarro to end the eighth. Closer Sergio Romo won a 12-pitch battle with Bruce, then struck out Scott Rolen to wrap it up. It was a team effort, made possible by Posey.

"He's a leader on this club," Bochy said. "He leads by example. He's a calming influence. You saw him go to the mound just to slow guys down, and the strikeout and throwing the guy out at third, that's a turning point."

And that's why there are foil wrappers and discarded corks and champagne stains on the carpet in the visitors' clubhouse at Great American Ball Park, where the party was supposed to be down the hall.